Outermost right parenthesis ) miscolouring
When you edit a formula, your parentheses may be temporarily mismatched. If you have more ) than ( and then add ( to balance the parentheses, then the ) of the outermost set of parentheses will have the same colour as the 2nd outermost set rather than be coloured black.
For example, type =()) into the formula bar and add a ( to make it =(()).
This miscolouring can add to the confusion of editing a large formula.
Excel Help commented
Overall, the coloring is very hard to follow. It's not in my wheelhouse to know what is easiest for the eyes/brain to decipher (leave it to the PhD's and graphic artists), I just know that for a lot of long formulas, the only way I can understand them is copy+pasting into notepad and separating out the elements with indentation.